(i) Field of the Invention
This invention relates to bilayer electronically-conducting films which are coated on electrodes and to processes for their production. This invention also relates to bilayer electronically-conducting films which have been stripped from the electrode so-coated.
(ii) Description of the Prior Art
The production of films on electrodes is old. Many such films were electrically non-conducting. For example, U.S. Pat. No. 1,904,418, patented Apr. 18, 1933 by C. Dantsizen, provided an insulating film on conductors in motors by making the winding the anode and then passing an electric current through an electrolyte, using a part of the stator itself or any other suitable conductor as the cathode.
U.S. Pat. No. 4,295,951, patented Oct. 20, 1981, by T. Bommaraja et al, provided a film-coated cathode for the electrolysis of alkali metal halide solutions in the substantial absence of chromium ions. The cathode comprised a conductive substrate, e.g. titanium, steel, iron, or alloys thereof, coated with an adherent, porous film of a substantially-electrically-non-conductive material having an average coating thickness of less than 10.sup.3 microns. Such material was said to be chemically inert in the halate solution.
U.S. Pat. No. 3,477,924, patented Nov. 11, 1961, by R. S. Gregorian et al, provided an electropolymerization process for foming a polyarylene oxide by maintaining an electric potential between electrodes immersed in a basic aqueous solution of a hydroxylated aromatic compound. The electrically-conductive polymer was said to be recoverable as a coating on the anode.
Carbazole-based materials, e.g., polycarbazoles, are well known in the prior art as photoconductive materials. Many photoconductive elements have been prepared which used such polyvinyl carbazoles and related materials. The prior art contains a large body of patents and articles concerned with the preparation and use of materials prepared from carbazoles. Polyvinylcarbazole polymers prepared from N-vinylcarbazole have been found to function in a useful manner in photoconductive layers. The prior art has also been concerned with electrophotographic materials of this type formed by substitution by various constituents on aromatic portions of the carbazole molecule.
U.S. Pat. No. 4,111,850, patented Sept. 5, 1978, by W. D. Kwalwasso, provided carbazole-based, molecular, photoconductive charge-transfer complexes which were easily applied to electrode substrates. The carbazole-based complexes coprised 3-substituted carbazoles complexed with an electron acceptor molecule, e.g. 2,4,7-trinitrofluorenone. The patentee also provided methods for contructing photoconductive elements on thin, semitransparent flexible substrates, the photoconductors being applied from solution or suspension in a fast drying liquid onto an electrode assembly attached to a flexible plastic substrate.
U.S. Pat. No. 4,386,987, patented June 7, 1983 by M. J. Covitch et al provided a method of forming a membrane upon an electrode from a dispersed, perfluorocarbon copolymer. The perfluorocarbon polymer was dispersed in a solvating medium, a substantial portion being solvated. The dispersion was applied to an electrode and the dispersion medium was removed.
The prior art has also been concerned with electrically-conductive polymer films. U.S. Pat. No. 4,461,691, patented July 24, 1984 by A. J. Frank provided electrodes overcoated with electrically-conductive polymer films. The electrodes typically comprised an inorganic semiconductor overcoated with a charge-conductive polymer film comprising a charge-conductive polymer in or on which was a catalyst or charge-relaying agent.
U.S. Pat. No. 4,476,003, patented Oct. 9, 1984 by A. J. Frank et al provided a method of coating electrodes with electrically-conductive polymer films. The charge-conductive polymer was covalently or coordinatively attached to the surface of the electrode to strengthen the adhesion characteristics of the polymer to the electrode surface or to improve charge-conductive properties between the conductive polymer and the electrode surface. Covalent or coordinative attachment was said to be achieved by a number of alternative methods including covalently or coordinatively attaching the desired monomer to the electrode by means of a suitable coupling reagent and, thereafter, electrochemically polymerizing the monomer in situ.
Polymer-coated electrodes have gained considerable attention for two reasons. An electrically-conducting polymer film on an electrode is believed to be useful for a particular chemical reaction over a wide range of potentials and hence may reduce unwanted side reactions. It is further believed that such film is itself catalytic or can easily absorb a catalyst and so can accelerate a desired reaction in some circumstances. It is also believed that the deposited polymer may be both electronically-conducting and an ion-exchange membrane, or may be only electronically-conducting. Both of these forms of conductivity are believed to be essentially functional diodes, (i.e. they conduct charge in only one direction) or may give some degree of rectification.